1. Technical Field
The present invention relates to a technology for displaying an image by using a projector.
2. Related Art
Advances of today's image-related technologies are remarkable, and any flat image can be displayed on a large screen at significantly high definition. Further, a variety of technologies that allow unaided eyes with no special glasses to view a three-dimensional image that gives a sense of depth have been developed.
For example, it is a known fact that we achieve a sense of depth by using the difference in vision between the left and right eyes (what is called parallax). Taking advantage of the above fact, JP-A-2008-003172 proposes a technology that allows unaided eyes to view a three-dimensional image that gives a sense of depth by preparing a left-view image and a right-view image and simultaneously projecting the left-view image from the left and the right-view image from the right on a screen, such as a folding screen, having irregularities provided at fine intervals.
It is known that we also use brightness information to achieve a sense of depth. To this end, two translucent screens are overlaid but spaced apart by a predetermined distance, and an image showing the same scene is projected on the two screens, the one on the near side and the other one on the remote side. In this setting, a near subject in the image is projected on the near screen at higher brightness, whereas the same subject is projected on the remote screen at lower brightness. Conversely, a remote subject in the image is projected on the remote screen at higher brightness, whereas the same subject is projected on the near screen at lower brightness. JP-A-2007-288317 proposes such a technology for displaying a three-dimensional image that gives a sense of depth by displaying the same image on near and remote screens but changing the brightness of the images on the two screens.
The proposed technologies of the related art, however, are problematic in that it is still difficult to display a three-dimensional image without any sense of strangeness. Such a sense of strangeness likely becomes more significant when an enlarged image is displayed. The reason for this follows: First, to achieve a sense of depth, we combine a variety of types of information, for example, not only the parallax and brightness information but also information associated with focusing operation that the eyes perform when viewing an object, orientation of the eyeballs (what is called the angle of convergence), and change in vision when the view point is shifted (what is called motion parallax). Therefore, when a sense of depth is expressed based on a certain type of information (parallax between the left and right eyes, for example), the viewer notices a discrepancy between the sense of depth obtained from the above certain type of information and that obtained from another type of information (brightness, for example), resulting in a sense of strangeness. Further, when an enlarged image is displayed, the angle at which the viewer looks at a central part of the image greatly differs from the angle at which the viewer looks at a periphery of the image. It is therefore difficult for the viewer to achieve a sense of depth at the periphery. As a result, the viewer recognizes a large discrepancy between the two types of sense of depth, and sometimes feels a significant sense of strangeness.